Ocrim1967 - Senza Titolo

(Source)

Take me back to California 🌴❤️

(Source)

In 40 million years, Mars may have a ring (and one fewer moon)

Nothing lasts forever - especially Phobos, one of the two small moons orbiting Mars. The moonlet is spiraling closer and closer to the Red Planet on its way toward an inevitable collision with its host. But a new study suggests that pieces of Phobos will get a second life as a ring around the rocky planet.

A moon - or moonlet - in orbit around a planet has three possible destinies. If it is just the right distance from its host, it will stay in orbit indefinitely. If it’s beyond that point of equilibrium, it will slowly drift away. (This is the situation with the moon; as it gradually pulls away from Earth, its orbit is growing by about 1.5 inches per year.) And if a moon starts out on the too-close side, its orbit will keep shrinking until there is no distance left between it and its host planet. The Martian ring will last for at least 1 million years - and perhaps for as long as 100 million years, according to the study.

The rest of Phobos will probably remain intact, until it hits the Martian surface. But it won’t be a direct impact; instead, the moonlet’s remains will strike at an oblique angle, skipping along the surface like a smooth stone on a calm lake.

This has probably happened before - scientists believe a group of elliptical craters on the Martian surface were caused by a small moon that skidded to its demise. (If this were to happen on Earth, our planet’s greater mass would produce a crash as big as the one that wiped out the dinosaurs, the researchers noted as an aside.)

source

images: NASA/JPL, Tushar Mittal using Celestia 2001-2010, Celestia Development Team.

Asperitas and Mammatus

Well-defined, wave-like structures in the underside of the cloud; more chaotic and with less horizontal organization than the variety undulatus. Asperitas is characterized by localized waves in the cloud base, either smooth or dappled with smaller features, sometimes descending into sharp points, as if viewing a roughened sea surface from below. Varying levels of illumination and thickness of the cloud can lead to dramatic visual effects.

Occurs mostly with Stratocumulus and Altocumulus

Mammatus is a cellular pattern of pouches hanging underneath the base of a cloud, typically cumulonimbus rainclouds, although they may be attached to other classes of parent clouds.

source | source | images: x, x, x, x, x, x, x

NASA’s New Planet Hunter Reveals a Sky Full of Stars

NASA’s newest planet-hunting satellite — the Transiting Exoplanet Survey Satellite, or TESS for short — has just released its first science image using all of its cameras to capture a huge swath of the sky! TESS is NASA’s next step in the search for planets outside our solar system, called exoplanets.

This spectacular image, the first released using all four of TESS’ cameras, shows the satellite’s full field of view. It captures parts of a dozen constellations, from Capricornus (the Sea Goat) to Pictor (the Painter’s Easel) — though it might be hard to find familiar constellations among all these stars! The image even includes the Large and Small Magellanic Clouds, our galaxy’s two largest companion galaxies.

The science community calls this image “first light,” but don’t let that fool you — TESS has been seeing light since it launched in April. A first light image like this is released to show off the first science-quality image taken after a mission starts collecting science data, highlighting a spacecraft’s capabilities.

TESS has been busy since it launched from NASA’s Kennedy Space Center in Cape Canaveral, Florida. First TESS needed to get into position, which required a push from the Moon. After nearly a month in space, the satellite passed about 5,000 miles from the Moon, whose gravity gave it the boost it needed to get into a special orbit that will keep it stable and maximize its view of the sky.

During those first few weeks, we also got a sneak peek of the sky through one of TESS’s four cameras. This test image captured over 200,000 stars in just two seconds! The spacecraft was pointed toward the constellation Centaurus when it snapped this picture. The bright star Beta Centauri is visible at the lower left edge, and the edge of the Coalsack Nebula is in the right upper corner.

After settling into orbit, scientists ran a number of checks on TESS, including testing its ability to collect a set of stable images over a prolonged period of time. TESS not only proved its ability to perform this task, it also got a surprise! A comet named C/2018 N1 passed through TESS’s cameras for about 17 hours in July.

The images show a treasure trove of cosmic curiosities. There are some stars whose brightness changes over time and asteroids visible as small moving white dots. You can even see an arc of stray light from Mars, which is located outside the image, moving across the screen.

Now that TESS has settled into orbit and has been thoroughly tested, it’s digging into its main mission of finding planets around other stars. How will it spot something as tiny and faint as a planet trillions of miles away? The trick is to look at the star!

So far, most of the exoplanets we’ve found were detected by looking for tiny dips in the brightness of their host stars. These dips are caused by the planet passing between us and its star – an event called a transit. Over its first two years, TESS will stare at 200,000 of the nearest and brightest stars in the sky to look for transits to identify stars with planets.

TESS will be building on the legacy of NASA’s Kepler spacecraft, which also used transits to find exoplanets. TESS’s target stars are about 10 times closer than Kepler’s, so they’ll tend to be brighter. Because they’re closer and brighter, TESS’s target stars will be ideal candidates for follow-up studies with current and future observatories.

TESS is challenging over 200,000 of our stellar neighbors to a staring contest! Who knows what new amazing planets we’ll find?

The TESS mission is led by MIT and came together with the help of many different partners. You can keep up with the latest from the TESS mission by following mission updates.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com. 

10 Things: How to Photograph a Meteor Shower

Taking photographs of a meteor shower can be an exercise in patience as meteors streak across the sky quickly and unannounced, but with these tips – and some good fortune – you might be rewarded with a great photo.

These tips are meant for a DSLR or mirrorless camera, but some point-and-shoot cameras with manual controls could be used as well.

1. The Photo Op: Perseids Meteors

The Perseids are dusty remnants of comet 109P/Swift-Tuttle.

Earth passes through the comet’s invisible, multi-billion mile trail of tiny debris each year around August, creating a meteor shower of so-called “shooting stars” as the particles are vaporized in our atmosphere.

Perseid meteors already are streaking across the sky. This year’s shower peaks on a moonless summer night -from 4 pm on the 12th until 4 am on the 13th Eastern Daylight Time.

Read more on the Perseids ›

2. Get away from city lights and find a place with dark skies.

In this 30 second exposure, a meteor streaks across the sky in Spruce Knob, West Virginia, during the 2016 Perseids meteor shower. Credit: NASA/Bill Ingalls

Too much light and it will be hard for your eyes to see fainter meteors, plus your image will get flooded with the glow of light. Turning down the brightness of the camera’s LCD screen will help keep your eyes adjusted to the dark. The peak of the 2018 Perseid meteor shower occurs just after the new moon, meaning a thin crescent will set long before the best viewing hours, leaving hopeful sky watchers with a moonlight-free sky!

3. Use a tripod.

In this ten-second exposure, a meteor streaks across the sky above Washington, DC during the 2015 Perseids meteor shower, Credit: NASA/Joel Kowsky

Meteor photography requires long exposures, and even the steadiest of hands can’t hold a camera still enough for a clear shot. Heavier tripods help reduce shaking caused by wind and footsteps, but even a lightweight tripod will do. You can always place sandbags against the feet of the tripod to add weight and stability. If you don’t have a tripod, you might be able to prop your camera on or up against something around you, but be sure to secure your camera.

4. Use a wide-angle lens.

In this 30 second exposure taken with a circular fish-eye lens, a meteor streaks across the sky during the 2016 Perseids meteor shower as a photographer wipes moisture from the camera lens Friday, August 12, 2016 in Spruce Knob, West Virginia. Credit: NASA/Bill Ingalls

A wide-angle lens will capture more of the sky and give you a greater chance of capturing a meteor in your shot, while a zoom lens captures a smaller area of the sky. The odds of a meteor streaking past that small patch are lower.

5. Use a shutter release cable or the camera’s built-in timer.

Long exposures are not just for meteors. In this shot taken at Joshua Tree National Park, a hiker’s headlamp leaves a trail of light along a twilight path. Credit: National Park Service / Hannah Schwalbe

A tripod does a great job of reducing most of the shaking your camera experiences, but even the act of pressing the shutter button can blur your extended exposure. Using the self-timer gives you several seconds for any shaking from pressing the shutter button to stop before the shutter is released. A shutter release cable (without a self-timer) eliminates the need to touch the camera at all. And if your camera has wifi capabilities, you might be able to activate the shutter from a mobile device.

6. Manually focus your lens.

In this 30 second exposure, a meteor streaks across the sky during the annual Perseids meteor shower Friday, August 12, 2016 in Spruce Knob, West Virginia. Credit: NASA/Bill Ingalls

At night, autofocus will struggle to find something on which to focus. Setting your focus to infinity will get you close, but chances are you’ll have to take some test images and do some fine tuning. With your camera on a tripod, take a test image lasting a few seconds, then use the camera’s screen to review the image. Zoom in to a star to see how sharp your focus is. If the stars look like fuzzy blobs, make tiny adjustments to the focus and take another test image.

Repeat until you are happy with the result.

If your camera has a zoomable electronic viewfinder or live view option, you might be able to zoom to a star and focus without having to take a test image.

7. Aim your camera.

The Perseids appear to radiate from the constellation Perseus, visible in the northern sky soon after sunset this time of year.

Even though we don’t know when or where a single meteor will appear, we do know the general area from which they’ll originate.

Meteor showers get their name based on the point in the sky from which they appear to radiate. In the case of the Perseids, during their peak, they appear to come from the direction of the constellation Perseus in the northern sky.

8. Calculate your exposure time.

In this 20-second exposure, a meteor lights up the sky over the top of a mountain ridge near Park City, Utah. Even though this image was captured during the annual Perseid meteor shower, this “shooting star” is probably not one of the Perseid meteors, which originate from material left behind by Comet Swift-Tuttle. Instead, it’s likely one of the many bits of rock and dust that randomly fall into the atmosphere on any given night. Credit: NASA/Bill Dunford

As Earth rotates, the stars in the sky appear to move, and if your shutter is open long enough, you might capture some of that movement. If you want to avoid apparent star movement, you can follow the 500 Rule. Take 500 and divide it by the length in millimeters of your lens. The resulting number is the length of time in seconds that you can keep your shutter open before seeing star trails. For example, if you’re using a 20 mm lens, 25 seconds (500 divided by 20) is the longest you can set your exposure time before star trails start to show up in your images.

9. Experiment!

In this 30 second exposure photo, hikers find their way to the top of Spruce Knob in West Virginia to view the annual Perseids meteor shower, Friday, August 12, 2016. Credit: NASA/Bill Ingalls

Once you know the maximum exposure time, you can set your shutter priority to that length and let the camera calculate other settings for your first image. Depending on how the image turns out, you can manually adjust aperture (set it to a lower number if the image is too dark) and ISO (set it to a higher number if the image is too dark) to improve your next images. Changing only one setting at a time will give you a better understanding of how those changes affect your image.

10. Enjoy the show.

The crew of the International Space Station captured this Perseid meteor falling to Earth over China in 2011. Credit: NASA

With your camera settings adjusted, capturing that perfect photo is just a matter of time and luck. The highest rate of meteors visible per hour is in the hours after midnight and before dawn. Set up your camera next to a lounge chair or a blanket to witness the wonder of a meteor shower for yourself – and, with any luck, you’ll take home some envy-inducing shots, too!

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.

Ask Ethan: Why Are There Only Three Generations Of Particles?

“It is eminently possible that there are more particles out there than the Standard Model, as we know it, presently predicts. In fact, given all the components of the Universe that aren’t accounted for in the Standard Model, from dark matter to dark energy to inflation to the origin of the matter-antimatter asymmetry, it’s practically unreasonable to conclude that there aren’t additional particles.

But if the additional particles fit into the structure of the Standard Model as an additional generation, there are tremendous constraints. They could not have been created in great abundance during the early Universe. None of them can be less massive than 45.6 GeV/c^2. And they could not imprint an observable signature on the cosmic microwave background or in the abundance of the light elements.

Experimental results are the way we learn about the Universe, but the way those results fit into our most successful theoretical frameworks is how we conclude what else does and doesn’t exist in our Universe. Unless a future accelerator result surprises us tremendously, three generations is all we get: no more, no less, and nobody knows why.”

There are three generations of (fermionic) particles in the Universe. In addition to the lightest quarks (up and down), the electron and positron, and the electron neutrino and anti-neutrino, there are two extra, heavy “copies” of this structure. The charm-and-strange quarks plus the top-and-bottom quarks fill the remaining generations of quarks, while the muon and muon neutrino and anti-neutrino plus the tau and tau neutrino and anti-neutrino comprise the next generation of leptons.

Theoretically, there’s nothing demanding three and only three generations, but experiments have shown that there are no more to within absurd constraints. Here’s the full story of how we know there are only three generations.

He faced all this for you, for you to be loved, blessed, glorified, exalted, satisfied, accepted, freed and resurrected.